How can I view my 3D rendered 360 pictures on gear VR?
This might be helpful:

How to render an environment to a Cube Map in Cycles

There is a section about rendering an "Equirectangular Map to Cube Map".
You can also download .blend files that come with the 3D camera and a compositing setup which seems to be pretty well documented.

I do not know of a way to view spherical images. You can view equirectangular images in the Samsung Internet Browser with some html biolerplate but the resolution really makes this a non-viable option.

Turning your scene into a Cube Map allows you to upload the file for viewing in the Oculus Photos app and it is the best solution in regards to quality.

The only downside is that you need to modify the cubemap image to follow the Oculus format which differs from what the Blender Internal mechanism expects.